Physics Physics - Section 3

Angular momentum, (rarely, moment of momentum or rotational momentum) is the momentum due to the rotation or revolution of matter.

It is, in effect, a vector giving a measure of the quantity of rotation in the matter, accounting for its mass, speed of rotation, and shape.

Compound (or catadioptric) telescopes, which use a combination of lenses and mirrors, offer compact tubes and relatively light weight; two popular designs are called Schmidt-Cassegrains and Maksutov-Cassegrains.

Rolling friction or rolling drag, is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy needed for deformation of the wheel, roadbed, etc. is recovered when the pressure is removed.

Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy.

Ballistics is the science of mechanics that deals with the launching, flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.

A ballistic body is a body with momentum which is free to move, subject to forces, such as the pressure of gases in a gun or a propulsive nozzle, by rifling in a barrel, by gravity, or by air drag.

A light-emitting diode (LED) is a two-lead semiconductor light source. It is a pn-junction diode, which emits light when activated.

When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons.

This effect is called electroluminescence, and the colour of the light is determined by the energy band gap of the semiconductor.

As seen from the Earth, a solar eclipse is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks ("occults") the Sun.

This can happen only at new moon, when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy.

Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method of determining the age of an object containing organic material by using the properties of carbon-14, a radioactive isotope of carbon.

Supersonic speed is a rate of travel of an object that exceeds the speed of sound (Mach 1).

Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic.

Flight during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.23

Sir Chandrasekhara Venkata Raman, FRS was an Indian physicist, born in the former Madras Province, whose ground breaking work in the field of light scattering earned him the 1930 Nobel Prize for Physics.

Henri Becquerel was a physicist, Nobel laureate, and the discoverer of radioactivity, for work in this field he, along with Marie Curie and Pierre Curie, received the 1903 Nobel Prize in Physics.

The SI unit for radioactivity, the becquerel (Bq), is named after him.